— 154 — 



here the reaction in the cold proceeds easily, and the total chlorine 

 escapes immediately in the form of hydrogen chloride. 



Protocatechuic aldehyde carbonate (m. p. 124 ) forms rhombic 

 crystals, and distils at 162 (13 mm. pressure), or at 289 at atmospheric 

 pressure. Boiling with v/ater leads in a few minutes to quantitative 

 loss of carbonic acid; if 4 parts solution of common salt are used, 

 the protocatechuic aldehyde produced separates out completely on 

 standing in the form of brilliant white crystals. 



Citral. C. Harries and A. Himmelmann 1 ) report on the 

 behaviour of the two isomeric citrals when treated with ozonised 

 oxygen. When working in petroleum ether solution, bright syrups 

 separate out, which in the dry state form viscid, slightly explosive 

 oils. They correspond to the formula C 10 H 16 O 5 , but are probably 

 not uniform monozonides of the above formula, but mixtures of 

 normal ozonides C 10 H 16 O 4 (principally), with normal diozonides of 

 the formula C 10 H 16 O 7 . This is also showed by their behaviour 

 towards sodium bicarbonate, and also towards water. When heated 

 with water they split up into hydrogen peroxide, laevulic aldehyde, 

 and another aldehyde which could not be identified. The occurrence 

 of acetone peroxide was also observed. Bromine in glacial acetic 

 acid was decolorised by the ozonides; they are consequently unsaturated 

 compounds. The authors conclude from these results that chiefly the 

 ozonide of the formula 



(CHA:C CH.CH 2 .CH 2 .C:CH.CHO 



I.—J I 



0:0:0 CH 3 



is formed. Diozonides of the two citrals a and b are formed when 



working in dry carbon tetrachloride. The also form thick syrups, 



which become solid on standing in vacuo, but do not decolorise 



bromine. When heated with water they split up into acetone peroxide, 



acetone, Isevulic aldehyde, and probably glyoxal, which latter the 



authors were, however, unable to identify with certainty. 



(CH 8 ) 2 :C CH.CH 2 .CH 2 .C CH-CHO 



0:0:0 CH 3 0:0:0 =CH 3 .CO.CH 8 



+ OCH.CH 2 .CH 2 .CO.CH 3 + OHC.CHO. 



Owing to the great popularity of the natural as well as the 

 synthetic violet preparations in the perfumery trade, further efforts 

 are constantly made to produce synthetically new products which 

 possess the characteristic, delightful violet odour. But up to the 

 present it has not yet been possible to produce a substance which 



*) Berl. Berichte 40 (1907), 2823. 



